Background: Justice-involved Veterans (i.e., those detained by or under the supervision of the criminal justice system) are a highly vulnerable population with multiple health needs (e.g., mental health [MH], substance use disorders [SUD]), and risk for criminal justice recidivism and homelessness). This may be especially true for Iraq and Afghanistan Veterans who often have complex MH and physical health needs. Moreover, Iraq and Afghanistan Veterans demographically differ from other war cohorts served at the Veterans Health Administration (VHA): many are younger, and many are women. Justice-involved Veterans who served in Iraq and Afghanistan (hereafter called OJIVs) will potentially be tomorrow's long-term VHA patients. There is an urgent need to develop interventions that improve their entry to and engagement in MH/SUD services, so as to address their MH care needs and to break the cycle of homelessness and criminal recidivism. Objectives: This research aims to improve utilization of VHA care by: (1) Identifying predictors of entry to and engagement in VHA MH/SUD care among OJIVs with a need for such care, (2) Evaluate OJIVs' experiences connecting to VHA MH/SUD care, and (3) Develop and pilot-test an intervention to increase entry to/engagement in VHA MH/SUD care among OJIVs. Methods: Based on Andersen's Behavioral Model and Life Course Theory, the current proposal will use quantitative and qualitative methods to inform the development of an intervention to improve entry to/engagement in VHA MH/SUD care among OJIVs. The first study will utilize VHA administrative databases and existing survey data to identify delivery system (Objective 1.1) and patient-level (Objective 1.2) predictors of entry to/engagement in VHA MH/SUD care. The quantitative findings will inform Objective 2 which will evaluate OJIVs experiences connecting to VHA MH/SUD care from the justice system. Semi-structured interviews with key informants, including VHA leadership, VHA providers, justice system representatives, and community groups will help characterize entry/engagement barriers experienced by OJIVs (Objective 2.1). Select key informants will be tapped to form an Advisory Board to validate results and guide intervention development. Additionally, narrative and semi-structured interviews with OJIVs will be used to identify barriers to/facilitators of entry to and engagement in VHA MH/SUD care (Objective 2.2). Results from the quantitative (Objective 1) and qualitative (Objective 2) studies will be used to develop and pilot-test an intervention in Objective 3 to support OJIVs in improving their entry to/engagement in VHA MH/SUD care. Patient-centered feedback will be solicited through focus groups (Objective 3.1) before pilot-testing with OJIVs (Objective 3.2). Career Development: Research activities accompanied by collaborations with operational partners and training activities that capitalize on mentors' expertise will provide a solid foundation for the PI's long-term research and career goals. (1) Content: Justice-involved Veterans (Mentor: Smelson; Consultant: Binswanger); Mental Health Services (Mentors: Frayne, Timko, Smelson); Women's Health (Mentor: Frayne). (2) Methods: VHA Databases (Mentors: Frayne, Asch); Quantitative Methods (Consultant: Sox-Harris); Qualitative Research (Consultant: Koenig); Intervention/Implementation (Mentors: Timko, Asch). The outlined research and training plan will promote the PI's development as an independently-funded VA health services researcher with expertise in conducting quantitative and qualitative evaluations and developing and implementing interventions for justice-involved Veterans and other vulnerable populations, such as homeless Veterans, served by VHA.